JP4272628B2 - Image forming roller - Google Patents

Description

  The present invention relates to an image forming roller used in an image forming unit of an image forming apparatus based on an electrophotographic system such as a copying machine, a printer, and a facsimile, and more particularly to an image forming roller including a resin shaft.

In an image forming unit of an image forming apparatus based on an electrophotographic system such as a copying machine, a printer, and a facsimile, an image forming roller related to image forming such as a transfer roller, a toner supply roller, a developing roller, and a cleaning roller is used. Conventionally, such an image forming roller has a configuration in which a conductive elastic layer is provided on the outer periphery of a metal shaft. However, in recent years, due to demands for reducing the size and weight of image forming apparatuses, the shaft is made of resin. Attempts have been made to form with compositions. For example, Patent Document 1 and Patent Document 2 disclose a nonmagnetic developing roller made of a resin composition containing a synthetic resin such as polyamide and a conductive agent, and optionally fibers. Patent Document 3 discloses a developing roller having a shaft made of a conductive resin composition containing a polyamide resin and a conductive material.
JP 2001-215780 A JP 2003-195601 A Japanese Patent Laid-Open No. 2002-40798

  However, as described in Patent Document 2 described above, the conventional resin-based shaft is only made by foaming a conductive elastic material in a mold provided with the resin-based shaft, or a foamed conductive elastic material. Is formed into a predetermined shape, and then the conductive elastic layer is provided only by adhering it to the resin shaft, or as described in Patent Document 3, a semiconductive material is coated on the resin shaft. However, there is no problem if the semiconductive layer is provided only by covering the outer periphery of the resin shaft with a conductive elastic material by extrusion, etc., and then supporting the shaft with the journal portion of the resin shaft, When the conductive elastic material is polished to form the conductive elastic material, the resin shaft is broken at the journal during polishing, and the image forming roller cannot be created. Jill it was revealed by the present inventors.

  Accordingly, an object of the present invention is to provide an image forming roller that has a resin-based shaft and is not damaged by polishing of a conductive elastic material.

According to the present invention, a resin composition comprising a shaft and a conductive elastic layer provided so as to cover the outer periphery of the shaft and polished, wherein the shaft includes aromatic polyamide, glass fiber, and a conductive material. The resin composition may further contain an aliphatic polyamide, and the glass fiber is 10 parts per 100 parts by mass in total of the aromatic polyamide and the aliphatic polyamide in the resin composition. The conductive material is contained in a proportion of ˜300 parts by mass, and the conductive material is contained in a proportion of 0.1 to 20 parts by mass, and the shaft exhibits a bending strength of 250 MPa or more and a bending elastic modulus of 15 GPa or more. An image roller is provided.

  According to the present invention, there is provided an image forming roller that has a resin-based shaft and is not damaged by polishing of a conductive elastic material.

  Hereinafter, the present invention will be described in more detail.

  The image forming roller of the present invention has a shaft formed of a resin composition containing aromatic polyamide, glass fiber, and conductive material particles, and a conductive elastic layer is provided on the outer periphery of the shaft.

  The shaft of the image forming roller of the present invention exhibits a bending strength of 250 MPa or more and a bending elastic modulus of 15 GPa or more. If the bending strength and flexural modulus are less than these values, cracks will occur when a conductive elastic layer such as conductive rubber is provided on the shaft and then the conductive elastic layer is ground and polished with a grindstone. obtain.

  The shaft of the image forming roller of the present invention preferably further exhibits a glass transition point of 70 ° C. or higher. The image forming roller is usually assembled as a unit and stored at about 60 ° C. in a stressed state. Further, the journal part may be heated to a temperature of about 60 ° C. during the cutting process. When the glass transition point is less than 70 ° C., there is a possibility that deflection occurs during the storage, and deformation occurs during the cutting process, which may reduce the surface accuracy.

  The shaft of the image forming roller of the present invention preferably further exhibits a specific gravity of 1.8 or less. If the specific gravity exceeds 1.8, there is a possibility that the request for weight reduction cannot be sufficiently met.

Furthermore, the shaft of the image forming roller of the present invention preferably exhibits a volume resistivity of 1 × 10 ⁵ Ω · cm or less. The volume resistivity exceeding 1 × 10 ⁵ Ω · cm is higher than the resistance value required for the conductive elastic layer provided on the outer periphery of the shaft, which may adversely affect printing.

  As described above, the shaft having the above physical properties is formed from a resin composition that includes aromatic polyamide, glass fiber, and conductive material particles, and may further include aliphatic polyamide.

  The aromatic polyamide is a polyamide having an aromatic group in the main chain, and is obtained by a polycondensation reaction between metaxylylenediamine and an α, ω-aliphatic dicarboxylic acid such as adipic acid, succinic acid, glutaric acid or pimelic acid. It is obtained. An aromatic polyamide obtained from metaxylylenediamine and adipic acid is known as polyamide MXD6.

  The aliphatic polyamide has a polycondensate structure of polymethylene diamine such as hexamethylene diamine and an aliphatic dicarboxylic acid, and includes polyamide 6, polyamide 6,6 and the like.

  As the glass fiber, those known per se can be used. The diameter of the glass fiber is preferably 1 to 50 μm, and the length is preferably 0.1 to 10 mm.

  As the conductive material, carbon black such as channel black, furnace black, thermal black, lamp black, ketjen black, and acetylene black, carbon fiber, and the like can be suitably used. The diameter of the carbon fiber is preferably 1 to 50 μm, and the length is preferably 0.1 to 10 mm. As the conductive material, carbon black and carbon fiber can be used in combination.

  The resin composition has 10 to 300 parts by weight of glass fiber and 0.1 to 20 parts by weight of conductive material for 100 parts by weight of the total of aromatic polyamide and aliphatic polyamide in order to bring the physical properties to the shaft. It contains in the ratio. The mass ratio of the aromatic polyamide and the aliphatic polyamide is preferably 100: 0 to 50:50.

  The shaft of the image forming roller of the present invention can be formed by a method such as injection molding. After injection molding, the journal part can be finished by cutting. More specifically, the image forming roller of the present invention has a roller body and journal portions integrally provided at both ends of the roller body.

  The conductive elastic layer provided on the outer periphery of the shaft body is based on a rubber material such as silicone rubber, acrylonitrile butadiene rubber, urethane rubber, ethylene propylene rubber, etc. In order to impart conductivity to this, conductive material such as carbon black or metal powder is used. It can be formed of a conductive rubber material containing a substance. The conductive elastic layer is formed by coating a conductive rubber material on the outer periphery of the shaft body and then polishing and grinding with a grindstone or the like by a conventional method. Alternatively, the conductive elastic layer can also be formed by adhering a tube body made of a conductive elastic material to the outer periphery of the shaft body and polishing and grinding the tube body by a conventional method. In either case, the polishing is performed while supporting the shaft having the conductive elastic material provided on the outer periphery of the main body with both journal portions and rotating the shaft. The thickness of the final conductive elastic layer (after polishing) is 0.2 mm or more from the viewpoint of polishing accuracy. The thickness of the conductive elastic layer after polishing is usually 10 mm or less.

  A microporous coating layer disclosed in JP-A-11-242383 can be provided on the outer periphery of the conductive elastic layer. This microporous coating layer is obtained by subjecting a reaction mixture containing a pore forming agent including a polyol, an isocyanate compound, and a volatile silicone oil to reaction conditions of the polyol and the isocyanate compound. The microporous coating layer is formed without the foaming phenomenon, and therefore does not require a mold necessary for normal foaming. The reaction mixture can also include a reactive silicone oil having active hydrogen. By providing such a microporous coating layer, when the image forming roller of the present invention is a developing roller, it is possible to more effectively prevent the photosensitive drum from being contaminated and negative ghosts.

  The image forming roller of the present invention can be provided as a transfer roller, a toner supply roller, a cleaning roller, etc. in addition to a developing roller.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Examples 1-4, Comparative Examples 1-3
Mitsubishi gas chemical polyamide MXD6 as an aromatic polyamide, Mitsubishi Engineering Plastics Novamid (registered trademark) 1007J as an aliphatic polyamide, Asahi Fiber Glass CS03-JAFT2 as a glass fiber, and Mitsubishi Chemical as a carbon black Using # 3050B, a shaft having a diameter of 14 mm and a surface length (rubber processed portion) of 235 mm was injection-molded from the resin composition having the composition shown in Table 1 below, and the journal portion was finished by cutting. Brother HL-1850 printer HL-1850 A resin shaft used as a developing roller was obtained. The obtained shaft was measured for flexural modulus, bending strength, glass transition point, specific gravity, and surface resistance. The results are shown in Table 2. The flexural modulus and flexural strength were measured with a strograph V10-C manufactured by Toyo Seiki Seisakusho, the glass transition point was measured with a thermal analyzer DSC-60 manufactured by Shimadzu Corporation, and the specific gravity was an electronic hydrometer MD manufactured by Alpha Mirage. The volume resistivity was measured with a resistance meter R8340 manufactured by Advantest Co., respectively.

  Furthermore, the runout of each shaft was measured by a conventional method. That is, when the shaft is supported by the journal and the shaft is rotated, the maximum and minimum values of the displacement of the shaft at the center in the longitudinal direction of the shaft are measured optically using a laser, and the difference between them is measured. It was calculated as a shake. The results (before standing at high temperature) are also shown in Table 2. The shaft runout after being left at high temperature was also measured. That is, each shaft was supported by a journal portion, a 1 kg load was applied to the central portion of the shaft, and the shaft was allowed to stand at 55 ° C. for 5 days. The results (after standing at high temperature) are also shown in Table 2.

Next, a conductive silicone rubber having a volume resistivity of 10 ⁶ Ω · cm and a JIS A hardness of 45 ° was coated on the outer circumference of each shaft, and this was polished to produce a rubber-coated roller having an outer diameter of 20 mm.

  The shaft runout after polishing of the silicone rubber layer was measured by the above method. The results are also shown in Table 2. At the time of polishing the silicone rubber layer, the rubber-coated roller having the shaft of Comparative Example 1 has cracks in the shaft itself regardless of the polishing conditions, or the rubber layer cannot be ground uniformly due to the deflection of the shaft. The developing roller could not be obtained. Further, the shaft of Comparative Example 2 could be polished somehow by greatly changing the polishing conditions. However, the shake after polishing was as extremely large as 0.2 mm (see Table 2).

  Next, 300 parts by weight of butyl acetate was added to 100 parts by weight of fluorine-containing polyol (Daikin Kogyo Co., Ltd.) and 5 parts by weight of conductive carbon black (Cabot Co., Ltd.), and dispersed using a disperser. To this dispersion, 5 parts by weight of volatile silicone oil (KF96L manufactured by Shin-Etsu Chemical Co., Ltd.) was added and stirred to obtain a main agent. A coating material in which urethane-modified hexamethylene diisocyanate (Duranate manufactured by Asahi Kasei Kogyo Co., Ltd.) as a curing agent is blended with this main agent so that the equivalent of the hydroxyl group in the main agent and the equivalent of the isocyanate group in the curing agent are 1: 1. A was prepared. This coating material A is spray-coated on each rubber-coated roller to a thickness of 10 μm, air-dried, and then heated at 160 ° C. for 40 minutes to form a desired microporous coating layer to obtain a developing roller. It was.

  The obtained developing roller was incorporated into a printer HL-1850 manufactured by Brother Industries, Ltd., and a paper passing test of 3000 sheets was performed to evaluate an image. The results are also shown in Table 2.

As is clear from the results shown in Table 2, the shafts of Examples 1 to 4 show a bending elastic modulus of 15 GPa or more and a bending strength of 250 MPa or more, so that the runout after polishing the coated rubber layer is small and clear. A developing roller that gives a clear image can be provided, and the shake after standing at high temperature is small.

Claims (7)

A shaft and a conductive elastic layer that is provided so as to cover the outer periphery of the shaft and is polished; and the shaft is formed of a resin composition containing aromatic polyamide, glass fiber, and a conductive material, and the resin The composition may further contain an aliphatic polyamide, and the glass fiber is in a ratio of 10 to 300 parts by mass with respect to 100 parts by mass in total of the aromatic polyamide and the aliphatic polyamide in the resin composition. And the said electroconductive material is contained in the ratio of 0.1-20 mass parts, The said shaft shows the bending strength of 250 Mpa or more, and the bending elastic modulus of 15 GPa or more, The imaging roller characterized by the above-mentioned.   The image forming roller according to claim 1, wherein the shaft further exhibits a glass transition point of 70 ° C. or more.   The image forming roller according to claim 1, wherein the shaft further exhibits a specific gravity of 1.8 or less. The image forming roller according to claim 1, wherein the shaft further exhibits a volume resistivity of 1 × 10 ⁵ Ω · cm or less.   The image forming roller according to claim 1, wherein the conductive material includes carbon black. The image forming roller according to claim 1, wherein a mass ratio of the aromatic polyamide to the aliphatic polyamide is 100: 0 to 50:50 .   The conductive elastic layer includes, as an elastic material, a rubber material selected from the group consisting of silicone rubber, acrylonitrile butadiene rubber, urethane rubber, and ethylene propylene rubber. The image forming roller described in the item.